Electron beam apparatus with aberration corrector

Abstract

An electron beam apparatus with an aberration corrector using multipole lenses is provided. The electron beam apparatus has a scan mode for enabling the operation of the aberration corrector and a scan mode for disabling the operation of the aberration corrector and the operation of each of the aberration corrector, a condenser lens, and the like is controlled such that the object point of an objective lens does not change in either of the scan modes. If a comparison is made between the secondary electron images of a specimen in the two modes, the image scaling factor and the focus remain unchanged and evaluation and adjustment can be performed by distinctly recognizing only the effect of the aberration corrector. This reduces the time required to adjust an optical axis which has been long due to an axial alignment defect inherent in the aberration corrector and an axial alignment defect in a part other than the aberration corrector which are indistinguishably intermingled with each other.

1. An electron beam apparatus with an aberration corrector, said apparatus comprising:
 an electron optical system which has at least an electron gun for emitting an electron beam, a condenser lens, an objective lens for converging an electron beam onto a surface of a specimen, and a scanning deflector for causing the converged electron beam to scan the surface of the specimen; 
 said aberration corrector composed of a plurality of combined multipole lenses; and 
 a computer for controlling at least one of the electron optical system and said aberration corrector, said computer having a first scan mode for enabling operation of said aberration corrector and a second scan mode for disabling the operation of said aberration corrector and controlling said objective lens, said condenser lens, or said aberration corrector such that an object point of the objective lens does not substantially change in either of the modes. 
 
     
     
       2. An electron beam apparatus with an aberration corrector, said apparatus comprising:
 an electron optical system which has at least an electron gun for emitting an electron beam, a condenser lens, an objective lens for converging an electron beam onto a surface of a specimen, and a scanning deflector for causing the converged electron beam to scan the surface of the specimen; 
 said aberration corrector composed of a plurality of combined multipole lenses; and 
 a computer for controlling at least one of the electron optical system and said aberration corrector, said computer having a first scan mode for enabling operation of said aberration corrector and a second scan mode for disabling the operation of said aberration corrector and controlling said objective lens, said condenser lens, or said aberration corrector such that an object point of the objective lens does not substantially change in either of the modes by switching a magnetization intensity of said condenser lens in association with ON/OFF modes of the aberration corrector. 
 
     
     
       3. An electron beam apparatus with an aberration corrector according to  claim 1 , wherein in said second scan mode, operation of said multipole lenses is disabled. 
     
     
       4. An electron beam apparatus with an aberration corrector according to  claim 2 , wherein in said second scan mode, operation of said multipole lenses is disabled. 
     
     
       5. An electron beam apparatus comprising:
 an electron optical system which has at least an electron gun for emitting an electron beam, a condenser lens, an objective lens, and a scanning coil; 
 an aberration corrector composed of a plurality of combined multipole lenses; and 
 a computer controlling at least one of the electron optical system and the aberration corrector, 
 wherein said computer has a ON mode for enabling operation of said multipole lenses and a OFF mode for disabling the operation of said multipole lenses and controlling at least one of the electron optical system and the aberration corrector such that an object point of the objective lens does not substantially change in either of the modes. 
 
     
     
       6. An electron beam apparatus according to  claim 5 , wherein said computer controls said objective lens, said condenser lens, or said aberration corrector such that said object point of the objective lens does not substantially change in either of the modes. 
     
     
       7. An electron beam apparatus according to  claim 5 , further comprising a mechanism for detecting a secondary electron and a reflected electron and forming an image in said ON mode for enabling operation of said multipole lenses and in said OFF mode for disabling the operation of said multipole lenses. 
     
     
       8. An electron beam apparatus according to  claim 5 , wherein said computer controls at least one of said electron optical system and said aberration corrector based on an image which detects secondary electrons or reflected electrons in said ON mode for enabling operation of said multipole lenses and in said OFF mode for disabling the operation of said multipole lenses.